With the increasing requirements for environmental protection and energy saving, for the power supply device in a standby mode or in a load state close to the standby mode (referred to as a light load state), skip mode control (or called burst mode control) is one of the solutions commonly used for improving an efficiency of the power supply device in the light load state. Most of the existing power supply devices have the function of the skip mode control.
An external system (i.e., an external load) may have a corresponding efficiency requirement and a power characteristic requirement of the load within a specific load range. For example, ripples may need to be reduced within the specific load range. Said efficiency requirement may be improved by the skip mode control. However, when the efficiency of the power supply device operating in the skip mode is significantly higher than the efficiency requirement of the load, the load of the power supply device within the mentioned specific load range may lead to a negative impact instead (e.g., noises being generated or ripples being amplified inside the load or the power supply device). Consequently, the power characteristic requirement of the load cannot be satisfied. Therefore, in order to satisfy the power characteristic requirement of the load, a balance between the efficiency of the power supply device and an efficiency required by the load must be controlled.